It has long been known that roadway marking materials can be adhered to roadway surfaces such as concrete and asphalt by means of pressure sensitive adhesives. EP 91 309 941 discloses a pavement marking material comprising a top layer, an optional base sheet and layer of adhesive wherein the adhesive comprises a rubber and a high-loading of tackifier. Such adhesives have been found to exhibit exceptional impact shear resistance. U.S. Pat. No. 3,902,939 (Eigenmann) discloses a pavement marking tape material which utilizes an adhesive which is not tacky at room-temperature but which is activated by a hot primer layer or solvent to provide adhesion to pavement surfaces.
It is also known from many branches of adhesion science that wet or damp surfaces are very difficult to adhere to. Adhesion to wet roadway surfaces for the purpose of either temporary or permanent marking of traffic lanes, for example, continues to be problematic, especially in regions where road surfaces are often damp or wet during a large part of the year.
Currently, adhesion to these substrates is typically improved somewhat by two means. Often a flame torch is used to dry the roadway--a labor intensive and thus expensive process. Commonly, a polymeric primer in organic solvent is brushed or sprayed onto the surface before the pressure sensitive adhesive-coated pavement marking is applied. From U.S. Pat. No. 4,906,523 (Bilkadi et al.), primers such as organosols are known. Furthermore, the use of solutions of high molecular weight rubbers in organic solvents as primers are known. Problems still exist, however, in that traffic markings applied to damp surfaces using these primers continue to separate from the roadway after short exposures to traffic and continued weathering.
As known primer systems there are used synthetic rubber-based pressure sensitive adhesives in organic solvents. In these pressure sensitive adhesive systems a mixture of a rubber like styrene-isoprene-styrene block copolymers and resin materials of terpene-based aliphatic hydrocarbon resins are used. Usually solvent systems are used, because rubber and resin components must typically be dissolved in different solvents. By combining the different solvents it could be possible that the system becomes incompatible, for example, by partial precipitation of the solids or phase separation and the like. A further drawback of the use of a solvent systems is that the priming composition itself might be altered, for example, due to the preferred evaporation of one of the solvents. Here also problems arise based on incompatibility of the solvents of the rubber or the resin respectively.
Another system is based on a neoprene rubber in different organic solvent systems, however, these neoprene high molecular weight rubbers are difficult to be kept in solution. A further system is known consisting of polybutadiene and bitumen in non-polar aliphatic hydrocarbon solution. Still another system is a rubber-based pressure sensitive adhesive in a chlorinated hydrocarbon such as methylene chloride. We believe that these systems described above do not address the problem of providing improved adhesion to wet and dry road surfaces.